With climate change, today's '100-year floods' may happen every three to 20 years

[phantom power]

I recall a neat little article in SciAm a couple decades ago where they showed how a fairly small translation of a distribution's mean results in small changes to the probability of events near the mean, but much larger probability increases at the tail of the distribution. So, the probability of common events will increase by a small fraction, but the probability of extreme events will double or triple. The farther out on the tail, the larger the ratio of the increase.

Last August, Hurricane Irene spun through the Caribbean and parts of the eastern United States, leaving widespread wreckage in its wake. The Category 3 storm whipped up water levels, generating storm surges that swept over seawalls and flooded seaside and inland communities. Many hurricane analysts suggested, based on the wide extent of flooding, that Irene was a “100-year event”: a storm that only comes around once in a century.

However, researchers from MIT and Princeton University have found that with climate change, such storms could make landfall far more frequently, causing powerful, devastating storm surges every three to 20 years. The group simulated tens of thousands of storms under different climate conditions, finding that today’s “500-year floods” could, with climate change, occur once every 25 to 240 years. The researchers published their results in the current issue of Nature Climate Change.

http://www.physorg.com/news/2012-02-climate-today-year-years.html

[Jackpine Radical]

1. Or, in simple statistical terms,

the variance increases much faster than the mean.